refer this
Dim oDevice As New SQLDMO.BackupDevice
Dim BACKUP As New SQLDMO.BACKUP
Dim SERVER As New SQLServer
Private Sub Form_Load()
On Error Resume Next 'If the device already exists an error will result if you try to add it again so just resume next cos its already there
With oDevice
.Type = SQLDMODevice_DiskDump
.Name = "NorthwindBakUp"
.PhysicalLocation = "C:\Documents and Settings\Administrator\Desktop\BACKUP.bak"
End With
SERVER.Connect "Sanjib", "sa"
SERVER.BackupDevices.Add oDevice
BACKUP.Action = SQLDMOBackup_Database
BACKUP.Database = "Northwind"
BACKUP.Devices ="NorthwindBakUp"
BACKUP.BackupSetDescription = "Full BackUp"
BACKUP.BackupSetName = "By Sanjib"
BACKUP.SQLBackup SERVER
End Sub
http://social.msdn.microsoft.com/Forums/en/sqlsmoanddmo/thread/1bef2612-6820-4ddd-bb64-087d0bc9d93d